Thin plastic bags are the ultimate throwaway item. Used once to tote groceries, the thin white bags often go on to second lives as permanent pollution and an eyesore. So a host of countries, cities and other governments have banned them or forced consumers to pay for them. The largest such country, by far, was China.

Even government officials admit the thinnest plastic bags, which were banned outright, are still in use, particularly in remote areas. Small workshops that churn out the contraband bags are easy to set up and hard to police. Small vendors, for their part, seem to think that the rule is no longer enforced and hand them out even in Beijing.

Yet, a survey by the International Food Packaging Association found that the number of plastic bags making their way into garbage had declined by 10 percent over the last year and the Chinese government claimed that supermarkets alone reduced such bag use by 66 percent—some 40 billion fewer plastic bags to get caught in trees, riverbanks or elsewhere. The ultimate hope of the Chinese authorities is for the bags that are used to be recycled.

Plastic bags may not disappear anytime soon but they're getting harder to spot.